There are many instances wherein electronic computers and more recently microprocessors are used to assimilate information from sensors, stored data, etc. and compute an accurate quantity of liquid flow for the most efficient and/or proper operation of a system or process using such liquids. For example, in fuel management systems for internal combustion engines of an automobile, currently on-board computers are supplied with data from sensors monitoring various engine operating parameters such as speed, temperature, exhaust gas characteristics, etc. and determine the proper fuel-air ratio for fuel economy and efficiency, smoothness of engine operations and compliance with emission standards. The electrical control signals are applied to a solenoid controlled fuel injection valve, which typically is biased closed by a spring so that a large electrical current is required to open the valve. As another example, in chemical manufacturing processes, computers are used to analyze process conditions (temperature, pressure, flow rates, output product parameters, etc.) and produce control signals that require precise and accurate metering of a liquid constituent. Solenoid controlled mechanical valves, which have relatively slow responses, are used to control the flow of liquid constituents in the process.
In these examples it is clear that while modern electronic computers and microprocessors have been developed to provide highly accurate control signals for controlling liquid flow, the control devices per se have typically been a solenoid controlled mechanical valve. These solenoid type valves and fuel injectors have difficulty in accurately tracking electrical signals and delivering short liquid pulses mainly because of their large pintel mass, which is magnified in the case of springs biasing them closed. The leading edge, in particular, of the liquid pulse delivered to the utilization system is not sharp. In the case of solenoid controlled fuel injectors for internal combustion engines, the output nozzles, are very sensitive to fluid loading so that if a passageway to direct the output fuel pulse to specific port intake targets (such as the valve stem) were attached, the performance is severely degraded.
The basic objective of this invention is to provide an improved liquid metering device and method. Another objective of the invention is to provide a fluidic transducer controlled by an electronic computer. Another objective of the invention is to provide an improved bistable fluidic liquid metering device. A further objective of the invention is to provide a hybrid bistable fluidic liquid flow metering device which is controlled by signals from an electronic computer. Another objective of the invention is to provide a transducer for translating an electronic control signal to a fluid control signal.
According to the invention, a hollow channel member, filled with liquid, is coupled to a member which receives acceleration (and deceleration) movements, there being at least a component of such movements along the axis of said hollow channel member. The control signal-pressure wave created by this movement of the liquid along the axis thereof travels at 4000-5000 ft./sec. A bistable fluidic switching element coupled to receive the control signal permits the full switching capability of the device to be utilized. The movement of the hollow channel member is produced by an electronic computer which produces electrical control signals that are applied, in push-pull fashion to a coil in a magnetic field. In the preferred embodiment, the coil is coupled to the hollow channel member and the liquid therein, very much like a voice coil in the magnetic field of loud speaker. The bistable fluidic switch element has an interaction region-chamber of the type wherein the sidewalls converge to a common outlet, which outlet feeds liquid flowing therethrough to first and second output channels, one leading to the utilization device and one leading to the supply of liquid. The common outlet with the converging sidewalls isolates the interaction region-chamber from the output channels and the converging sidewalls generates feedback vortices for maintaining the liquid flowing in the channels on one of the sidewalls until switched by the fluidic signal. In this embodiment, there are a pair of control ports upstream at each side of the entrance of the liquid jet into the interaction region-chamber. The opposie ends of the hollow channel or tube members are coupled to the chamber downstream of the control ports. In the preferred embodiment, both hollow channel or tube members are moved simultaneously under the action of the magnetic forces. They are connected to their respective control ports and downstream couplings to the chamber such that when the coil is accelerated in one direction, the liquid flow is switched to one side of the interaction region-chamber and through the common outlet to a selected one of the output passageways and when the coil is accelerated in the opposite direction, the liquid flow is switched by the control signal-pressure wave to the opposite side of the interaction region-chamber and to the other output passageway. Thus, the fluid circuit is constructed to maintain continuous flow through the passages to clear any vapor or air. The liquid is not required to cool the magnetic elements (as in a solenoid controlled fuel injector, for example). Since the control signal-pressure wave is generated by movement of a relatively short segment of liquid filled channel members, the motive force required of the magnetic system is much smaller and the fluidic bistable switch responds rapidly and more accurately to the electronic signals thereby much more effectively utilizing the speed and accuracy of current electronic computers. Since the response is faster than solenoid controlled valve systems, the liquid flow pulses can be frequency modulated or pulse (liquid pulse) width modulated to achieve highly accurate metering. The signals from the computer can modulate the flow of liquid between the output passageways at any rate desired. Moreover, since the bistable fluid switch elements can be molded, the cost is less as compared to solenoid controlled valve elements which may require careful machining of valve seats and pintles, etc., relatively heavy coils and currents. Finally, the reliability of liquid metering devices made according to the present invention is improved since the only moving parts are the coil and hollow channel or tube members.